Szakáll Sándor - Jánosi Melinda: Minerals of Hungary (Topographia Mineralogica Hungariae 4. Miskolc, 1996)

known locality is in the vicinity of Telkibánya. Mines in this area were at their most glorious during the reign of King Sigismund (1387-1437). It was around this time that Telkibánya was declared a Free Royal City. A second period of glory was enjoyed by the mine in the 16th century when, as a result of investments by the Thurzó and Fugger families, Mária mine was opened with an adit at Veresvíz. After that, mining declined considerably, partly because of the discovery of gold and silver mines in America, and partly because of the advance of the Turks. According to legend, the final decline was caused by a mining disaster when the Veresvíz adit caved in burying several miners. The narrow shafts of Medieval mining are still visible on Fehér Füll and Kánya Hill. Disseminated gold occurs in the weathered and brecciated country rock, hidden in pyrite and in quartz-lined cavities as minute lamellae or as aggregates. Silver also occurs within the weathered rock, and in quartz lined lenses and cavities, primarily as silver sulfide minerals a few millimeters long (acanthite, proustite, pyrargyrite, freibergite, polybasite). Colourless transparent, or violet, quartz crystals, up to several centimeters in length, are found in rocks accompanying the ore lodes which were buried beneath the surface. The best localities for these crystals are on Kánya Hill and on Sintatető Hill (Fig. 17). The most common accessory minerals found in the cavities (apart from varieties of quartz), are jarosite as yellow powdery aggregates and adularia, a hydrothermal habit variety of orthoclase. In the mountains, there are several outcrops of Miocene rhyolite rocks. These often contain quartz, biotite and sanidine crystals, several millimeters long, formed during the main crystallisation phase. Cavities in the rhyolite contain fewer hydrothermal, and autopneumatolitic minerals compared with those found in andésites, although small hexagonal tablets of tridymite are fairly widespread. Lithophysic rhyolite, consisting of concentric layers of alkali feldspar and crystals of tridymite, together with chalcedony and opal, is quite common in this area (Fig. 18). Probably the prettiest varieties of coloured opal occur in these rhyolites, often in large irregular masses (up to 10 cm in size), which formed from hydrothermal solutions. The best specimens come from the region of Telkibánya and Nagyhuta.